1. Field of the Invention
The invention relates generally to apparatus for sorting articles, such as agricultural comestibles and manufactured products, according to their physical characteristics. More specifically, the invention pertains to devices which use laser beam generators and linear arrays of photo detectors to collect information about the size and configuration of articles. The invention also relates to devices which compare collected article information to predetermined criteria, make electronic sorting determinations, then segregate articles having like and kind characteristics from an article stream.
2. Description of the Prior Art
The prior art discloses a variety of article sizing and sorting devices using one or more light sources and respective photo detectors, arranged in spaced relation. Articles are passed between the light source and the detector, interrupting a light beam extending between the two. A shadow is thereby created on the photo detector, indicating the presence of the article. Information gained from successive sampling of the output of the photo detector is first stored and then subsequently compared to predetermined criteria, relating to physical aspects of the articles.
U.S. Pat. No. 5,865,990, granted to Novak et al., shows the use of a single laser generator, a lens, a single photo detector, and a processor for sorting imperfect rice grains from perfect grains. One embodiment shows the use of a cylindrical lens to produce a laser line from a single laser beam, for the exposure of multiple grains of rice.
U.S. Pat. No. 5,448,363, issued to Hager, teaches an apparatus for reflectively sorting comestibles, such as potatoes, using laser beams. Plural laser diodes and respective oscillating scanning mirrors, are arranged on a frame. The mirrors are directed radially and inwardly, toward a test zone, and are adapted periodically to scan a subject article. Articles free fall through an aperture near the test zone where they are exposed to the laser beams. The reflected light is detected by plural optical fibers, radially disposed around a ring on the frame. An optical ribbon extends circumferentially around the inside surface of the ring as well. Outputs from the optical fibers and the optical ribbon are fed to signal processing circuits.
In U.S. Pat. No, 3,930,994, to Conway et al., a method and an apparatus for inspecting and sorting produce are disclosed. The illuminating means includes a zirconium arc and a quartz-iodine tungsten light, in combination with a condensing lens for collimating the light. In an additional embodiment, two parallel beams are used for illuminating articles to be sorted. These beams are generated either by a single laser with a beam splitter, or a pair of lasers.
U.S. Pat. No. 4,490,801, granted to Hagan et al., illustrates an article sizing apparatus employing a plurality of LEDS as a light source, and a plurality of respective photo diodes as light detectors. The LEDS and detectors are arranged in two mutually perpendicular arrays, allowing multiple measurements of articles to be made in a single pass. The outputs of the detectors are delivered to a microprocessor, which stores and computes the detector output to make determinations of characteristics of the articles.
U.S. Pat. No. 4,549,272, to Hagan et al., shows an article sorting device including solenoid actuated paddle means to divert articles from an outlet conveyor belt into a container filled with articles of a like predetermined weight.
Lastly, in U.S. Pat. No. 5,141,110, issued to Trischan et al., an apparatus using collimating lenses is disclosed. The source of light in one embodiment is an incandescent bulb or a fluorescent light. In another embodiment, a single laser is used, eliminating the need for a collimating lens.
The above-described prior art has a number of operational characteristics which could be improved. For example, resolution, speed, accuracy, immunity from ambient light, immunity from contaminants such as dirt and water, and detection of misaligned articles are all areas where prior art sorting and sizing devices need improvement. The invention disclosed herein provides improved performance respecting all of these important aspects of operation, for sorting and sizing devices.
A laser-based, high-resolution, article sizing and sorting apparatus is disclosed. An input conveyor propels articles, such as comestibles or manufactured items, through a scanning station. The scanning station preferably includes first and second scanning means, arranged in orthogonal relation. Each scanning means features groups of laser line beam generators and respective linear arrays of photo detectors. Each group of laser generators is spaced from and parallel to its respective line of photo detectors. The components of the first scanning means preferably utilize horizontally oriented scanning beams, and the components of the second scanning means preferably utilize vertically oriented scanning beams. The area between the generators and the detectors defines a generally square and planar exposure window, through which articles are propelled in an unsupported condition during the scanning procedure.
Each line beam generator has a respective cylindrical lens for collimating its output into a plurality of parallel laser beams, directed across the exposure window. In one embodiment of the invention, three laser beam generators and their respective lenses are arranged in a line, each line extending six inches along two adjacent sides of the exposure window.
In the same embodiment of the invention, the complementary groups of the photo detectors include three linear arrays of detectors, arranged in end-to-end relation to span the other sides of the exposure window, opposite from a respective group of laser generators. The pitch, or numeric density of the detectors within the array determines the resolution of the sizing and sorting apparatus. In the preferred embodiment of the invention, adjacent photo detectors are quite close, on the order of 0.4 mm, or {fraction (1/64)}xe2x80x3 apart. This spacing provides the high resolution of spatial data needed for accurate measurements and determinations regarding the size and configuration of subject articles.
The photo detectors provide analog output signals which are sampled and integrated during a scanning cycle. These analog outputs are first conditioned, and then fed to A/D converters where they are transformed into a digital number. The digitized outputs of the converters are directed to a microprocessor and associated memory devices, where they are organized and stored during a scanning operation comprised of successive scanning cycles. Computer-based analyses and determinations are made regarding the size, configuration, and weight of the articles. Articles determined to satisfy predetermined physical characteristics are electronically tracked and eventually diverted onto respective conveyors, carrying articles having like characteristics.
Accordingly, one object of the present invention is provide a device capable of measuring the size and configuration of articles, quickly and with a high degree of accuracy.
Another object is to provide an optical sorting device which is substantially immune from erroneous determinations caused by exposure to ambient light.
Yet another object is to provide a weather tight and easy to clean housing, for the sensitive laser beam and optical detector elements of the sorter.
Yet another object of the present invention is to provide a sorting device which makes accurate determinations for article size, configuration, and weight, over extended periods of time and in dusty, field conditions.
Yet another object of the invention disclosed herein is to provide a sorting device capable of accurately calculating the correct width and length of an article as it passes through a scanning station at any angle.
And, another object of the invention is to provide electronic sorting apparatus which can be incorporated in newly constructed sorters, and also can be retrofitted to existing sorting devices to improve their performance and expand their operational features.